How does commit 47ec340c not introduce a bug?

Robin Holt
2013-05-07T09:17:34Z

I noticed a warning while cross-compiling all arm defconfigs.

The mmp2_defconfig gave this warning:

drivers/video/backlight/max8925_bl.c: In function 'max8925_backlight_probe':
drivers/video/backlight/max8925_bl.c:177:3: warning: statement with no effect [-Wunused-value]

This appears to have been introduced by the above commit when !CONFIG_OF

Looking at this more closely, I am not sure how this was ever intended
to be handled or how the errors returned in the CONFIG_OF case were
intended to be handled as the return from max8925_backlight_dt_init is
always ignored.

I think this needs some more attention, but do not feel like I know
enough about it or have any means to test it to weigh in.

Thanks,
Robin

commit 47ec340cb8e232671e7c4a4689ff32c3bdf329da
Author: Qing Xu <qingx@marvell.com>
Date: Mon Feb 4 23:40:45 2013 +0800

mfd: max8925: Support dt for backlight

Add device tree support in max8925 backlight.

Signed-off-by: Qing Xu <qingx@marvell.com>
Signed-off-by: Haojian Zhuang <haojian.zhuang@gmail.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

diff --git a/drivers/video/backlight/max8925_bl.c b/drivers/video/backlight/max8925_bl.c
index 2c9bce0..5ca11b0 100644
--- a/drivers/video/backlight/max8925_bl.c
+++ b/drivers/video/backlight/max8925_bl.c
@@ -101,6 +101,29 @@ static const struct backlight_ops max8925_backlight_ops = {
.get_brightness = max8925_backlight_get_brightness,
};

+#ifdef CONFIG_OF
+static int max8925_backlight_dt_init(struct platform_device *pdev,
+ struct max8925_backlight_pdata *pdata)
+{
+ struct device_node *nproot = pdev->dev.parent->of_node, *np;
+ int dual_string;
+
+ if (!nproot)
+ return -ENODEV;
+ np = of_find_node_by_name(nproot, "backlight");
+ if (!np) {
+ dev_err(&pdev->dev, "failed to find backlight node\n");
+ return -ENODEV;
+ }
+
+ of_property_read_u32(np, "maxim,max8925-dual-string", &dual_string);
+ pdata->dual_string = dual_string;
+ return 0;
+}
+#else
+#define max8925_backlight_dt_init(x, y) (-1)
+#endif
+
static int max8925_backlight_probe(struct platform_device *pdev)
{
struct max8925_chip *chip = dev_get_drvdata(pdev->dev.parent);
@@ -147,6 +170,13 @@ static int max8925_backlight_probe(struct platform_device *pdev)
platform_set_drvdata(pdev, bl);

value = 0;
+ if (pdev->dev.parent->of_node && !pdata) {
+ pdata = devm_kzalloc(&pdev->dev,
+ sizeof(struct max8925_backlight_pdata),
+ GFP_KERNEL);
+ max8925_backlight_dt_init(pdev, pdata);
+ }
+
if (pdata) {
if (pdata->lxw_scl)
value |= (1 << 7);
@@ -158,7 +188,6 @@ static int max8925_backlight_probe(struct platform_device *pdev)
ret = max8925_set_bits(chip->i2c, data->reg_mode_cntl, 0xfe, value);
if (ret < 0)
goto out_brt;
-
backlight_update_status(bl);
return 0;